Corvette LS3 Engine Build - One-to-One Relationship

In Part 2 Of Our Exclusive Coverage, We Help Button Up A Dry-Sump Ls3 And Run It Through A Battery Of Quality-Control Tests

If you recall from our last issue, Chevrolet asked us to go behind closed doors to participate in a dry-sump-LS3 engine build and document the process. The location of our assignment was GM's Performance Build Center (PBC), in Wixom, Michigan, a 100,000-square-foot facility capable of assembling up to 15,000 engines per year. PBC personnel currently hand-build the dry-sump LS3 used in manual Corvette Grand Sport coupes, as well as the Z06's LS7 and the ZR1's LS9.

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Last month, we showed you how a highly trained team of technicians assembles these halo engines-one at a time, one builder per engine-and documented the first steps in the build process. Come along now as we help install the heads, lifters, and rockers, and then watch the intake and ignition go on. After that, we'll see how the hand-built LS3 is leak-tested, watch as the exhaust manifolds, flywheel, and clutch assembly are installed, then follow the brand-new engine through weighing, quality control, cold testing, balancing, and final approval.

Along the way, you'll witness some of GM's proprietary engine-build techniques, many of which have never before been disclosed to the public. You won't have to take a vow of secrecy-just appreciate the craftsmanship that Chevy's master engine builders put into every one of these hand-built Corvette engines.

Due to the length of the build and the many steps involved, we'll be limiting our coverage to the highlights of the process. Rest assured, however, that the PBC engine techs put their formidable skills into every detail of every build, down to the most minor components.

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Corvette LS3 Engine Build - One-to-One Relationship

At the GM Performance Build Center (PBC), a highly trained team of technicians hand-assembles the LS7, LS9, and dry-sump LS3 engines. Here, (from left) production group leader Ken Ray and engine builders Ron Hein, Rich McBride, and Don Henley show off a freshly built dry-sump LS3. Follow along now to see how it all came together.

Cylinder-head gaskets sit in a kitting tray ready for the picking. Hein will don protective gloves before he reaches for a set of two-these things are sharp!

The gaskets go on the block's deck, one per cylinder bank, as seen here.

Hein wipes both cylinder heads' surfaces clean, and then mates them to the block.

He then inserts 10 large and 5 small bolts into the cylinder-head assembly by hand.

Hein uses a multi-spindle machine to anchor the heads in place. The machine simultaneously torques all 15 bolts in less than five seconds.

The multi-spindle machine leaves no room for error. All 15 head-bolt torques have to be within GM's strict tolerances, as indicated by the green light shown here. If any one of the bolts falls outside the torque-specification parameters, Hein uses the machine to back it out and re-torque it.

Hein grabs a kitting tray, which contains intake and exhaust rocker arms laid out as they'll be installed, bolts already in place. Notice that the pushrods are in a cup container to ensure that the correct quantities are in the kit. Two rocker-arm saddles are also included in the tray.

After installing the pushrods, Hein applies a little oil to their ends, as well as to the valve stems. Each time he applies oil to a component, it adds to the base weight of the engine. We'll see why this is important later in the story.

He then places the rocker arms in position and starts the bolts with a battery-powered handtool.

Here's how the rocker arms look after they've been installed in the head and loosely tightened.

This alignment guide holds the rockers in position, verifies that they're in the correct order, and shows the engine builder the specific rocker-bolt torque sequence he needs to follow.

The author takes his turn applying torque to the rocker-arm bolts.

Every intake-manifold assembly comes with the throttle body and MAF preinstalled. Hein just has to grab one from this crate place his name tag on the intake's right front surface, and install the intake on the engine (not shown).

Hein loosely assembles the rocker-arm covers followed by the water-pump assembly. (Note: After a part is loosely assembled on the engine, Hein goes back and torques its bolts with the computerized torque wrench described in last month's story.)

He then installs the balancer hub on the crank, using a hydraulic press set to around 4,000 psi.

Hein installs both coil packs and "finger starts" the studs.

With the engine almost ready for leak testing, Hein seats the spark plugs.

Hein secures the leak-test fixtures onto the engine. He then places seals over the exhaust ports, coolant passages, and crank flange.

Hein connects hoses to the water crossover and the PCV tube for both the oil and coolant circuits of the engine. He pressurizes the air to 20 psi on the coolant side and 2.5 psi on the oil side. Once pressure is built up, he takes a reading and measures pressure loss to determine the engine's leak rate.

Hein stamps a star on the block to signify that the engine has passed the leak test.

He then fastens the exhaust manifolds to the cylinder heads, first loosely by hand, and then with the computerized torque wrench shown here.

Clutch pressure-plate and disc assemblies sit in dunnage ready to be installed onto the engine.

Hein places the flywheel on a table and marks the balance holes to assist the balance-room operator. The holes are numbered according to crankshaft position, and the operator places weights into them depending on where the machine finds an imbalance (if at all).

Hein installs the flywheel on the engine at the last build station.

With that done, he installs the clutch assembly. Note how the clutch fingers are depressed as the pressure plate is installed.

Here's the engine assembly with the clutch fully installed. Hein weighs the engine dry (this one is 444.8 pounds) and then adds oil (20.7 pounds, in this example) to achieve a target weight before the finished assembly is shipped to Bowling Green. (Each engine's weight varies due to the amount of lubricant used in its construction. The amount of oil added is different from engine to engine to account for this variance.) Hein is holding up the engine-manifest sheet, which details every aspect of the build and is kept on file at the PBC for future reference.

Quality-control tests are next. Before the engine goes into the cold-test stand, PBC engine builder Rich McBride attaches fixtures to the exhaust manifolds, the throttle body, and the oil pan. He also places NVH (noise, vibration, and harshness) plugs in the cylinder heads and the block. (Note: PBC engine builders take turns performing the quality-control tests.)

McBride places the engine in the cold-test area and hooks up the required sensors. The cold-test operation measures oil pressure, exhaust pressure, intake vacuum, ignition, head and block noise/vibration, and engine-spinning torque. It also checks crank and cam sensors. All this information is fed into a database and compared with stored parameters to determine whether the engine is ready to ship.

Once the engine passes its cold test, PBC engine builder and balance-room operator Don Henley cycles it through the balance machine, using natural gas (instead of gasoline) for fuel. This machine finds imbalances in the front and rear of the engine. Henley then places weights on the damper pulley and the flywheel to bring the imbalances into specification. The specs call for less than 0.5 ounces/inch in both the front and the rear.

After all quality-control tests have been completed, author Phillip and engine builder Hein, pose with the ready-to-ship LS3 engine. When the engine leaves PBC, it will be sent to the Corvette Assembly Plant in Bowling Green, Kentucky, to be installed in a '10 or '11 Grand Sport manual coupe.

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